1. Field of the Invention
The present invention relates to a dishwasher, and more particularly, to a method for controlling a dishwasher having a water softener for changing a supplied washing water into a soft water.
2. Discussion of the Related Art
FIG. 1 is a view of a general dishwasher. Referring to FIG. 1, the dishwasher includes: a main body 2 having an opening at a front side; a door 4 openably installed on the front side of the main body 2; a washing tub 6 installed inside the main body 2, for washing dishes; a shelf 8 movably installed inside the washing tub 6, for receiving the dishes; a nozzle 10 rotatably installed in a lower side of the shelf 8, for spraying washing water through a spraying hole 10a; a sump 12 formed on a lower side of the washing tub 6, for collecting washing water; a washing pump (not shown) installed on one side of the sump 12, for pumping washing water through the nozzle 10; and a controller (not shown) installed inside the main body 2, for controlling an operation of the dishwasher.
At a lower side of the washing tub 6, the dishwasher further includes: a heater (not shown) for heating washing water supplied to the inside of the sump 12; a water supply device having a wafer supply passage 20 through which a supplied washing water flows and a water supply valve 22 for opening and closing the water supply passage 20; a drain device having a drain passage 30 through which a drained washing water flows and a drain pump 32 for draining washing water through the drain passage 30; and a water softener 40 for communicating with the water supply passage 20 and changing a supplied washing water into a soft water.
Also, the door 4 includes: a steam inlet port 4a for inhaling steam in the inside of the washing tub 6; a steam outlet port 4b for discharging the inhaled steam out of the door; and a ventilator 16 formed between the steam inlet port 4a and the steam outlet port 4b. 
Referring to in FIG. 2, a guide tub 50 is installed between the main body 2 and the washing tub 6. In the guide tub 50, the water supply passage 20, the drain passage 30 and an air inlet passage 18 for inhaling air from the outside are separated from one another.
An entrance of the water softener 40 is connected with the water supply passage 20 and the exit of the water softener 40 is connected with the sump 12.
An ion-exchange-resin reservoir 42 with a built-in ion-exchange resin 42a, a salt reservoir 44, a regeneration valve 46 are provided in the inside of the water softener 40. The regenerator valve 46 is formed between the salt reservoir 44 and the ion-exchange-resin reservoir 42 and prevents a regenerative water 44a from flowing into the ion-exchange-resin reservoir 42 from the salt reservoir 44.
Here, the ion-exchange-resin tank 42 is filled with the ion-exchange resin 42a for adsorbing/removing hard water component, such as heavy metal and metallic ion, thereby changing a washing water supplied from the sump 12 into a soft water having a good washability.
Also, the salt reservoir 44 is filled with salt. Therefore, if a predetermined amount of washing water is supplied to the salt reservoir 44 through the water supply passage 20, a salt water to be used as the regenerative water 44a is formed in the salt reservoir 44 and the regenerative water 44a is supplied to the ion-exchange-resin reservoir 42 through the regeneration valve 46, such that the ion-exchange resin 42a is regenerated. The controller controls the flowing of the regenerative water 44a and the regeneration of the ion-exchange-resin 42a by opening/closing the regeneration valve 46.
An operation of the dishwasher constructed as above will now be described. Referring to FIG. 3, the controller of the dishwasher opens the water supply valve 22 so as to supply a washing water along the water supply passage 20 to the sump 12 (ST1). Then, a washing water pumped by the washing pump 14 is sprayed through the spraying hole 10a of the nozzle 10, so that the dishes received in the shelf 8 are washed (ST2). A detergent is put into the washing tub 6 so that a dish washing operation is smoothly performed.
Also, a washing water flowing through the water supply passage 20 reacts with the ion-exchange resin 42a and a hard water component is removed, thereby increasing a detergent solubility of washing water. As a result, a washing performance of the dishwasher is improved. However, if the water softening reaction of washing water is performed continuously, the ion-exchange resin 42a is exhausted and the water softening performance of the water softener 40 is deteriorated. Therefore, if the washing step is completed, the controller regenerates the ion-exchange resin 42a by inputting regenerative water 44a into the ion-exchange resin 42a (ST3). In other words, the controller supplies a regenerative water 44a of the salt reservoir 44 to the ion-exchange-resin reservoir 42 by closing the water supply valve 22 and opening the regeneration valve 46.
Then, the ion-exchange resin 42a is regenerated by ion-exchange reaction of the ion-exchange resin 42a with the regenerative water 44a, recovering a water softening property of the washing water. Next, the controller supplies a washing water to the ion-exchange-resin reservoir 42 by closing the regeneration valve 46 and opening the water supply valve 22 and drains the hard water and regenerative water, which remain in the ion-exchange-resin reservoir 42 due to the supplied washing water, thereby washing the ion-exchange-resin reservoir 42 (ST3).
Also, the controller supplies a washing water from the water supply valve 22 to the sump 12. The washing water of the sump 12 is pumped by the washing pump and thus flows into the nozzle 10. Also, the washing water is sprayed through the spraying hole 10aof the nozzle 10, so that the washed dish is rinsed (ST4). In step ST4, the hard water component of the washing water supplied to the sump is removed by the water softener 40 and a detergent is not put into the washing tub 6. Then, the washing water in the inside of the washing tub 6 is completely drained to the outside by means of the drain device (ST5). The ventilator 16 installed in the door 4 operates to dry the inside of the washing tub 6 (ST6).
However, the dishwasher operating in this manner has a problem that deteriorates performance of the water softener. The reason is that the time required for regenerating the ion-exchange resin is not sufficient because the regeneration and washing steps (ST3) for regenerating and washing the ion-exchange resin at the water softener is performed between the washing step and the rising step. In other words, since the washing water for washing the ion-exchange resin is introduced at the time point when the introduction of the regenerative water for regenerating the ion-exchange resin is completed, reaction time for the ion-exchange resin and the regenerative water is not sufficient. Therefore, regeneration of the ion-exchange resin is not performed completely, thus degrading the water softening performance of the ion- exchange resin.
Also, the step of regenerating and washing the ion-exchange resin is performed according to a predetermined time regardless of a hardness value of washing water for washing the dishes. Therefore, in case the washing water has a high hardness, the hard water component still remains in the ion-exchange resin even after the step of regenerating and washing the ion-exchange resin, resulting in the degradation of the water softening performance of the ion-exchange resin: Particularly, since the hard water component remaining in the ion-exchange-resin reservoir 42 flows into the inside of the washing tank together with supplied washing water, the washed dishes is re-contaminated in the washing step or the washing performance of the dishwasher is deteriorated.